Conventional conveyor belts having energy-saving properties have employed a technique, for example, to reduce resistance for riding over by reducing energy loss of a bottom-surface-cover rubber.
To date, to provide a rubber composition for conveyor belts that can both achieve energy-saving properties and durability, a rubber composition for a conveyor belt, the rubber composition comprising:
(A) 100 parts by mass of a diene-based polymer, and
(B) from 25 to 55 parts by mass of a carbon black containing a carbon black (b-1) having a nitrogen adsorption specific surface area of 60 to 100 m2/g and a dibutyl phthalate oil absorption of less than 110 mL/100 g, and a carbon black (b-2) having a nitrogen adsorption specific surface area of less than 60 m2/g and a dibutyl phthalate oil absorption of 110 mL/100 g or greater, has been proposed (Japanese Unexamined Patent Application Publication No. 2013-122018A).
However, conventional rubber compositions for conveyor belts do not achieve sufficient energy-saving effects.
Furthermore, when a conveyor belt is operated, energy loss occurs in cases where the conveyor belt sags by the load as well as by the resistance for riding over or in cases where trough deformity is caused.
Furthermore, as physical properties of a rubber composition used in the top-surface-cover rubber layer of a conveyor belt, in addition to high fracture characteristics, hardness, and tear strength, high bending fatigue resistance is also required because of the large bending deformation caused by a pulley.